1. Field of the Invention
The present invention relates to an improvement in a tester which is employed for testing the resistance of fibers, dyed goods and paints, etc., to the effects of light and it includes means to make the surface temperature of the exposed surface of each sample uniform by providing a flow divider in the lower region of a sample-setting frame and thereby directing an air-flow for regulating the temperature and humidity toward the back sides of samples and the circumference of a radiation (or light) source (typical lamp is a xenon lamp) rather than toward the exposed surfaces of the samples, so that the light-resistance test is performed under the condition of uniform temperature of the samples themselves which is most important for obtaining valid results.
2. Prior Art
In a conventional light-resistance tester, as shown in FIG. 1, a light source such as a xenon lamp 1 is provided in a testing chamber, sample holders 3 are mounted on a sample-rotating frame 2 which rotates around the lamp 1, and light from lamp 1 is applied to samples 4 mounted in the sample holders. The light resistance of the samples is determined by observing the degree of fading. Since the air in the testing chamber rises due to heat from the light source during the test, outside air is introduced by a blower 5 into the testing chamber through an air inlet 6 at the upper part of the chamber and downwardly and through a constant humidity tank 8 so as to lower the temperature in the testing chamber. An air-baffle plate 9 is provided below the sample holders to divert the air laterally from inlet opening 5a to just beneath the inside surface of the sample holders 4 so that the air rises past the ends of the baffle plate 9 along the surfaces of the sample holders, i.e. the surfaces of the samples, from the circumference of the plate 9, and flows out through vent 6a.
When the temperature inside the testing chamber reaches a prescribed level, an air regulator 7 in the air inlet 6 moves to a position indicated by the dotted lines to close inlet 6 and stop the introduction of outside air, and consequently the air coming out of the testing chamber flows from the constant humidity tank 8 along the surfaces of the samples and back down through the blower in a continuous circulation. The air regulator 7 works also as a temperature regulator, and it is opened and closed to carry out the controlling operation.
Since the air from the blower flows along the surfaces of samples, the surface temperature of the samples is affected by the temperature of this air. When the air regulator 7 is set to introduce outside air, the temperature in the constant humidity tank falls, though only for a very short time. Consequently, the temperature of the air flowing along the surfaces of the samples falls temporarily and fluctuates. If the temperature of the outside air is 20.degree. C. when it is desired that the temperature in the testing chamber be adjusted to 40.degree. C., for instance, the surface temperature of the samples varies from 57.degree. to 59.degree. C., i.e. by 2.degree. C., due to the opening and closing of the air regulator, though only for a very short time. This is a first fault of the conventional light-resistance tester.
The air flowing over the surfaces of samples rises while being heated by a light energy from the xenon lamp 1. Hence, the temperature of the air is higher along the upper region of the samples and lower along the lower region thereof, and thus the temperature is not uniform in the upper and lower regions of the samples. Actual measurement has showed that there is a temperature difference of 5.degree. to 6.degree. C. between the upper and lower regions of the samples. This is a second fault of this tester.
A temperature difference also occurs between samples, and thus the temperature of all of them is not uniform. Studies by the present inventor disclosed that this non-uniformity was caused by the gaps formed between adjacent sample holders. When the sample holders are nearest to the air regulator 7, for instance, the circulating air flows through said gaps, and thus the air flowing over the surface of the sample, and hence the surface temperature, is not uniform. The temperature difference between samples is further increased by the presence or absence of said gaps and the difference in the dimensions thereof. This is a third fault of the conventional tester.
When there is a temperature difference between the surfaces of the samples, the color difference value representing the degree of fading due to the test varies, even if the light energy of the source (the xenon lamp) is applied at a prescribed strength and for the same time duration. Therefore, the step of changing the position of the sample holder or turning it over during the course of the test has been taken heretofore so as to reduce the effect of the non-uniformity of the temperature. Whether or not a light-resistance tester gives normal fading color difference values is examined by using xenon blue standard cloth which is issued by AATCC (American Association for Textile Chemists and Colorists). FIG. 2 shows the results of a test conducted for 20 sheets of this cloth. The U.L line indicates the standard value for the upper and lower portions of the sample, which value is 19.5, and M the standard value for the intermediate portion thereof, which value is 20.5. It is seen from this figure that measured values deviate considerably from the straight U.L line of standard fading color difference values and the straight M line thereof, and intersect these lines depending on the position of the same around the periphery of the sample rotating frame. The measured values are clearly not at all uniform.
As described above, the nonuniformity of the fading color difference is related to the nonuniformity of the temperature values. Thus, uniform temperature is a requisite for obtaining accurate results from the test.